Oxidatively stable esters



United States Patent 3,393,226 OXIDATIVELY STABLE ESTERS Brian Ronald David Whitear, London, England, assignor to The British Petroleum Company Limited, London, England, a corporation of England No Drawing. Filed Sept. 29, 1964, Ser. No. 400,242 Claims priority, application Great Britain, Oct. 11, 1963, 40,175/63 Claims. (Cl. 260479) ABSTRACT OF THE DISCLOSURE Novel esters of the following formula are provided CH OCO(CH COOC,H R

where R is a phenyl or phenoxy group and n. is an integer from 1 to 5, said esters having high oxidation stability and utility as lubricants and heat transfer fluid.

This invention relates to certain novel esters having high oxidation stability and utility as lubricants or heat transfer fluids.

The said novel esters are those of the general formula CH .O.CO (CH CO.O.C H .R (Formula I) where R is a phenyl or phenoxy group, preferably attached to the phenylene group in the ortho or meta position, and 11 1-5, preferably 2 or 3.

The invention also includes a method of preparing the esters described above, in which an acid halide of the formula:

CH .O.CO( CH CO.X

is reacted with a compound of the formula:

MO.C H .R

wherein:

X is a halogen atom M is an alkali metal atom, preferably a sodium or potassium atom, or a hydrogen atom,

R is a phenyl or phenoxy group, preferably attached to the phenylene group in the ortho or meta position, and

the reaction being conducted so as to eliminate a salt MX with the production of an ester as described above. The acid halides specified above may be prepared by refluxing the appropriate methyl half ester with thionyl chloride in the usual way. The methyl half esters can be isolated by suitable methods from the mixture of dibasic acid, half ester and diester obtained by reacting dibasic acid and diester under trans esterification conditions (see, for example, G. B. Brown et al., Journal of Organic Chemistry, volume 12, page 163 (1947)). The

succinic and glutaric half esters (n=2 and 3 respectively) can, however, be more conveniently prepared by "Ice reacting one molar proportion of the appropriate acid anhydride with one or more molar proportions of methanol followed by removal of the excess alcohol by distillation.

By way of example, the preparation of three esters according to the invention will now be described.

Ester A.Methyl o-phenylphenyl succinate Succinic anhydride g.) and methanol (50 g.) were heated under reflux for 2 hours. The excess solvent was a distilled off and the residue of the crude methyl half ester of succinic acid solidified (M.P. 50 C. approx). This material was treated with thionyl chloride (70 ml.) and the mixture was gently refluxed. The reaction mixture was distilled and the fraction boiling over the range 108-111 C./l5 mm. was taken as the acid chloride of the methyl half ester of succinic acid (yield: g.).

The sodium salt of o-phenylphenol (20 g.) was refluxed with the acid chloride of the methyl half ester of succinic acid (15 g.) in benzene and the reaction product was washed with dilute aqueous caustic potash, dried and distilled. The fraction boiling over the range 154- 158 C./0.l mm. was taken as methyl o-phenylphenyl succinate (yield: 25 g).

Ester B.Methyl m-phenoxyphenyl succinate m-Phenoxyphenol (24 g.) was refluxed with the acid chloride of the methyl half ester of succinic acid (20 g.) in benzene for 24 hours. The reaction product was washed with dilute aqueous caustic potash, dried and distilled. The fraction boiling over the range 174176 C./0.05 mm. was taken as methyl m-phenoxyphenyl succinate (yield: 31 g.).

Ester C.-Methyl m-phenoxyphenyl glutarate m-Phenoxyphenol (55.8 g.) was refluxed with the acid chloride of the methyl half ester of glutaric acid (44.6 g.) in benzene for 24 hours. The reaction product was washed with dilute aqueous caustic potash dried and distilled. The fraction boiling over the range l88-193 C./O.3 mm. was taken as methyl m-phenoxyphenyl glutarate (yield: 38 g.).

The oxidation stability of Esters A, B and C and of two other experimental ester lubricants for aero-tur-bine engines, X and Y, noted for their good high temperature oxidation stability properties, were assessed in a laboratory oxidation rig in which three litres per hour of air were passed through a 10 ml. sample of the oil contained in a tube kept for 12 hours in an oil bath at 260 C. The degree of oxidative breakdown of the esters is assessed by measuring the percent change in the kinematic viscosity of the ester at 210 F. and the acidity increase. In the case of esters X and Y, tests were also carried out on them after they had been inhibited with 2% wt. of iminodibenzyl, a known antioxidant for synthetic lubricants intended for use at very high temperatures. Results of the tests are given in the following table.

TABLE Viscosity Oxidation Test of ester Ester Antioxidant Boiling range of ester at 210 F. 210 F. Acidity (centistokes) viscosity increase,

change, percent mg. KOH/g.

A None 154-158 C. at 0.1 mm. Hg..." 4. 9 -4 1. 5 B do 174-176 C. at 0.5 nun. Hg 4. 37 +5 2. 5 C do 188193 C. at 0.3 mm. Hg 4. 29 +20 3.3 220 C. at 1 mm. Hg. 5.0 +295 25.75 220 C. at 1 mm. Hg. 7. 1 +2.5 20.3 X +70 12. 05 Y 10. 30

% WtIIDB 3 IDB=Iminodibenzyl. The outstanding oxidation stability of the esters according to the invention is clearly demonstrated.

Ester X was prepared by reacting together under 4 R is attached to the phenylene group in the ortho position.

3. An ester according to claim 1, in which the group R is attached to the phenylene group in the meta posiesterification conditions 28:10:1 molar mixture of 5 tion.

caprylic acid, trimethylolpropane and sebacic acid. Ester Y was prepared by reacting together under esterification conditions a 10:4:1 molar mixture of caprylic acid, trimethylolpropane and sebacic acid.

I claim: 1. Novel esters of the general formula:

CH .O.CO(CH C0.O.C H .R

where:

R is selected from the group consisting of phenyl and phenoxy groups, and

n is an integer from 15.

2. An ester according to claim 1, in which the group 4. An ester according to claim 1, in which n 2. 5. An ester according to claim 1, in which n=3.

References Cited UNITED STATES PATENTS 12/ 1962 Mills 260479 OTHER REFERENCES Ivashchenko et al.: Zh. Obshch Khim. 32 (1962),

15 3765-8. QD1Z6.

LORRAINE A. WEINBERGER, Primary Examiner.

M. WEBETER, M. G. BERGEN, Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION ratent No. 3,393,226 July 16, 1968 Brian Ronald David Whitear It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Columns 1 and 2, in the TABLE, fourth column, line 1 thereof,

"4.9" should read 4.99

Signed and sealed this 9th day of December 1969.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edw Fletcher, Jr.

' Commissioner of Patents Officer 

